docs: def add_scales_bar(img, bbox):
      """
      Add a scales bar to the  map.
  
      Calculates the resolution at the current latitude and
      inserts the corresponding scales bar on the map.
  
      Args:
          img (Image): Image object to which the scales bar will be added.
          bbox (TileBB): boundaries of the map
  
      """
      tc = TileCoordinate(bbox.min.zoom, bbox.min.x, bbox.min.y)
      meters_per_pixel = tc.resolution()
      one_km_bar = int(1000 * (1 / meters_per_pixel))
      col_black = (0, 0, 0)
  
      line_start = (100, img.size[1] - 100)  # px
      line_end = (line_start[0] + one_km_bar, line_start[1])
      whiskers_left = [line_start[0], line_start[1] - 15, line_start[0], line_start[1] + 15]
      whiskers_right = [line_end[0], line_end[1] - 15, line_end[0], line_end[1] + 15]
  
      draw = ImageDraw.Draw(img)
      draw.line([line_start, line_end], fill=col_black, width=5)
      draw.line(whiskers_left, fill=col_black, width=2)
      draw.line(whiskers_right, fill=col_black, width=2)
      draw.text((line_start[0] + 10, line_start[1] + 10), fill=col_black, text="1 km")
      del draw